Metal strand comprising interrupted filament

ABSTRACT

A metal strand ( 101 D) as subject of the invention comprising at least two filaments. At least one filament ( 105 ) is interrupted providing a filament end ( 107 A,  107 B), which is fixed to the uninterrupted filaments of the strand ( 101 D) using a fixing substance, preferably a soldering substance. Such strand can be used to provide e.g. cords, rubber or polymer reinforcement of tires and belt such as elevator or timing belts, hoisting or elevator ropes, control cables or suspension rope.

FIELD OF THE INVENTION

The present invention relates to metal strands and cords and more inparticular to maintain the workability of metal strands comprisingfilament ruptures present in the metal strand or cord.

BACKGROUND OF THE INVENTION

At present, it is a problem that during strand and cord construction,using e.g. double or single twisting operations, filaments of the strandor cord break. Most frequently, such ruptures cause two loose ends offilament, which projects out of the profile of the strand or cord.

The loose filament ends of the strand or cord may cause problems whenthe strand or cord is used during subsequent processes.

When such strand with projecting filaments is used to provide amulti-strand cord, these projecting filaments may cause process problemsduring cord production. The projecting ends may cause congestion ineyes, guiding parts or on small passages.

Due to this interaction between machinery parts and the filament ends,the broken or interrupted filament may “sleeve off”. Over a large lengthof the strand, the filament is pulled out of the strand.

When strands as such or cords with projecting filaments are used, e.g.as control cables, these projecting filaments may cause disorder of theprocess in which it is used.

When such strand or cord with projecting filaments is used to providepolymer or rubber products (e.g. timing belts, elevator or hoistingbelts), the projecting filaments may cause shearing or disfunctioning ofthe polymer or rubber matrix. Also here the projecting ends may causecongestion in guiding parts of e.g. extrusion machinery or othermachines processing the strands or cords.

Therefor, such strands or cords with broken filaments or with filamentends projecting out of the profile of the strand or cord are avoided.

In order to avoid such projecting filaments, metal strands or cords,comprising such projecting filament ends, may be cut into two at thelocation of the projecting filament ends. As a result, a strand or cordwith a length being the length of the strand or cord before the filamentrupture is provided.

Either strand ends or cord ends may be welded one to another, providinga welded strand or cord with a relatively equal profile at the weld.This is hereafter referred to as “end-to-end welded” strands or cords.This solution does provide a strand or cord, which has inferiormechanical properties e.g. a lower force at rupture, a lower elasticity(strain at rupture), and higher bending stiffness and lower torsionductility.

Although end-to-end welded metal strands can be used to provide cords, asacrifice on mechanical properties of the metal cord is made.

SUMMARY OF THE INVENTION

It is a subject of the invention to provide a metal strand, comprisinginterrupted metal filaments, not having filament ends projecting out ofthe profile of the strand, but which can be processed, in spite of thesefilament ruptures, without the risk of sleeving off. The metal strand assubject of the invention preserves the mechanical properties of themetal strand to a large extent.

A metal strand as subject of the invention comprises at least twofilaments, at least one filament is interrupted, providing at least onefilament end. According to the present invention, this filament end isfixed to the uninterrupted filaments of the strand using a fixingsubstance. The place where the filament ends are fixed to theuninterrupted filaments of the strand is hereafter referred to as“fixation point”.

Such filament interruptions may e.g. be caused by filament ruptures atthe twisting points in the double or single twisting operations or byfilament spools running empty or because of a rupture of the filament atthe creel containing the filament spools.

It is understood that usually, although not necessarily, a filamentinterruption provides two filament ends, each being fixed to theuninterrupted filaments of the strand using a fixing substance, at adifferent fixation points.

In such case, a certain interruption zone length may be defined as themaximum strand length, comprising the two fixation points. Usually thetwo filament ends don't meet one another anymore at the ends. It is evenso that most usually, the interruption zone has a length between severalmillimeters and several meters.

The fixing substance may be a glue or gluing paste, a polymer material,but preferably a soldering material. The solder is preferably providedusing Ag, Sn or an alloy of Sn and Ag.

In case glue is used, metal-to-metal glue is preferred. Temperature ofthe fixing substance during application, e.g. the melting temperature ofthe polymer or soldering material, is preferably lower than thetransformation temperature of the metal alloy of the filaments, in orderto preserve the mechanical and physical properties of the filaments.Most preferably, a temperature of less than 700° C., most preferablyless than 350° C. is used. E.g. when steel is used, this transformationtemperature is to be understood as the temperature above which the steelalloy transforms into an austenitic structure.

The fixation point preferably has a diameter, being less than 1.2 timesthe strand diameter or even more preferred, less than 1.1 times thestrand diameter. The fixation point preferably has a diameter, beingmore than 0.8 times the strand diameter or even more preferred, morethan 0.9 times the strand diameter. Most preferably, the fixation pointis essentially equal to the strand diameter.

“Strand diameter” is defined as the diameter of the smallest circleencompassing a radial cross-section of the strand. The diameter at thelocation where the filament ends being fixed to the m filaments presentin the interruption zone is the diameter of the smallest circleencompassing the location where the filament ends being fixed to the Mfilaments present in the interruption zone.

Preferably, the number of filament ends at each fixation point is lessthan 4, preferably less than 3 or less than 2. Most preferably only onefilament end is present in each fixation point.

A metal strand as subject of the invention has as an advantage that thefilament ends, being fixed to the uninterrupted metal filaments, don'tdisturb the use of such strands in further processes such as cablingprocesses or extrusion processes, e.g. by sleeving off.

Nor does the fixation of the filament ends at the ends of theinterruption zone, provide an inflexible zone to the metal strand, ascompared to the “end-to-end” welded strands. The metal strands assubject of the invention have also improved mechanical properties at thelocation where interrupted filaments are present, as compared to“end-to-end” welded strands.

Since preferably only a few or even one filament end is to be fixed at afixation point, the strand is not weakened too much. The breaking loadof the strand or cord, at the location of the interruption filament,approaches the sum of the breaking loads of the non-soldered metalfilaments in the metal strand.

The force at rupture of a sample of the metal strand as subject of theinvention is usually more than 50%, e.g. more than 60% or even more than80% of the force at rupture of a sample of the metal strand withoutinterrupted filaments. The elongation at rupture of a sample of themetal strand as subject of the invention is usually more than 30% e.g.more than 50 or even more than 60% of the elongation at rupture of asample of the metal strand without interrupted filaments. Since usuallyhigh security factors for strand loads are used, the presence of asoldering zone on strand level does not cause any additional risk.

When strands as subject of the invention are used to provide polymer orrubber products (e.g. timing belts, elevator or hoisting belts), therisk on shearing or disfunctioning of the polymer or rubber matrix isremoved, since no projecting filaments are present. Congestion inguiding parts of e.g. extrusion machinery or other machines processingthe strands is no longer present.

“Strand” is to be understood as a number of metal filaments, beingtwisted with each other, resulting in a strand having an outer surfaceconsisting of outer surface filaments. all outer surface filamentsprovide the outer surface of the strand. Possibly a core, alsocomprising metal filaments is provided to the strand. Such core has nofilaments being present at the outer surface of the strand.

As en example, a strand comprises two layers of metal filaments, onelayer providing a core and one layer providing the outer surface. Suchstrands are referred to as n×a+m×b-constructions, n and m being a numberof filaments, whereas a and b referring to the filament diameter,expressed in mm. e.g. 1×0.19+6×0.175 or 1×0.21+6×0.19. Usually, in casen or m equals 1, n or m is not mentioned in the name of the product.

The core itself may also be provided as a layered construction of metalfilaments. As an example, n₁*a₁+n₂*a₂+m*b construction is mentioned,comprising a core of a two-layered n₁*a₂+n₂*a₂-construction, aroundwhich a third, outer layer of m*b metal filaments is provided. n₁, n₂and m represent the number of filaments, whereas a₁, a₂ and b are therespective diameters of the filaments, expressed in mm. As an example,1*0.13+6*0.12+12*0.12 or 3*0.15+9*0.15+15*0.15 strands are mentioned.

The filament ends are fixed to the other uninterrupted filaments, eitherto one of the uninterrupted filaments, or to more than one of theuninterrupted filaments.

Metal strands as subject of the invention, preferably are provided outof steel alloys, most preferably out of carbon steels, having more than0.275% C or more than 0.4% C or even more than 0.6% C, or stainlesssteel alloys.

Possibly the strand comprises metal filaments all of an identicalfilament diameter. However, usually the filaments of a strand as subjectof the invention have different filament diameters. The diameters of themetal filaments are preferably less than 1.15 mm, e.g. less than 1.05 mmor less than 0.85 mm or even less than 0.7 mm, such as less than 0.5 mm,or less than 0.35 mm or even less than 0.25 mm, such as less than 0.21mm. As an example, the diameter of the metal filaments are larger than0.03 mm.

It is understood that a strand may comprise different filaments, whichare of e.g. a different diameter, a different alloy or have a differentcoating.

The strands as subject of the invention have a strand diameterpreferably less than 5 mm, e.g. less than 4 mm or less than 2.5 mm oreven less than 1.75 mm, such as less than 1.4 mm, or less than 0.9 mm oreven less than 0.7 mm, such as less than 0.6 mm or even less than 0.2mm. The strand diameter is the diameter of the smallest imaginarycircle, which encompasses the radial cross-section of the strand. As anexample, the strand diameter is larger than 0.04 mm.

Further, according to the present invention, a metal cord obtainable byusing at least one but preferably only one metal strand with filamentends being fixed to uninterrupted filaments as subject of the inventionmay be provided. Also, if during production of a metal cord, one or morefilaments of one of the strands of the cord breaks, fixation of filamentends to the uninterrupted filaments of this strand using a fixationsubstance may be applied.

In both cases, a metal cord comprises at least one strand as subject ofthe invention, having filament ends being fixed to the uninterruptedfilaments present in this strand.

A metal cord may have any cord construction comprising at least twostrands, each comprising at least two metal filaments.

As an example, ‘n×m-’constructions may be used, e.g. 3×3, 7×3, 4×7, 7×4,7×7 or 7×19. n is to be understood as the number of strands in the cord,each strand having m filaments. It is understood that each strand maycomprise different filaments, which are of e.g. a different diameter, adifferent alloy or have a different coating.

Also ‘m₁+(n×m₂)-’constructions may preferably be used. Around a corestrand of m₁ filaments, n strands of m₂ filaments are provided. Anexample is a 3+5×7-cord, being a cord comprising a core strand of 3filaments, around which 5 strands of 7 filaments each are provided. Thefilaments m₁ and m₂ may be of the same or a different diameter.

It is understood that each strand may comprise different filaments,which are of e.g. a different diameter, a different alloy or have adifferent coating.

A metal cord has a cord diameter preferably less than 14 mm, e.g. lessthan 12 mm or less than 9 mm or even less than 7 mm, such as less than 5mm, or less than 4 mm or even less than 2.5 mm, such as less than 2 mmor less than 1.7 mm, but may even be less than 0.25 mm. As an example,the cord diameter is larger than 0.10 mm.

“Cord diameter” is defined as the diameter of the smallest circleencompassing a radial cross-section of the cord. The diameter at theinterruption zone is the diameter of the smallest circle encompassingthe cross-section of the cord where the interruption zone of the strandas subject of the invention is present.

As the projecting filaments out of the profile of the cord may beavoided, the same benefits are obtained as for strands as subject of theinvention. No projecting filament ends may cause process interruption ordisturbance due to sleeving off, nor the mechanical properties of thecord are influenced to a large extent.

The force at rupture of a sample of the metal cord comprising a strandas subject of the invention is usually more than 75%, e.g. more than 80%or even more than 90% of the force at rupture of a sample of the metalcord without strand as subject of the invention. The elongation atrupture of a sample of the metal cord comprising a strand as subject ofthe invention is usually more than 30% e.g. more than 50 or even morethan 60% or even more than 70% such as more than 80% of the elongationat rupture of a sample of the metal cord without strand as subject ofthe invention. Since usually high security factors for cord loads areused, the presence of a strand as subject of the invention on strandlevel does not cause any additional risk.

The elongation at rupture of a sample of the metal cord comprising aninterruption zone is larger compared to the elongation at rupture of asample of the metal cord being welded over the whole cross-section ofthe cord.

When a cord comprising a strand as subject of the invention is used toprovide polymer or rubber products (e.g. timing belts, elevator orhoisting belts), the risk on shearing or disfunctioning of the polymeror rubber matrix is minimized. Congestion in guiding parts of e.g.extrusion machinery or other machines processing the cord is no longerpresent, meanwhile enjoying the improved mechanical properties.

Therefor metal cord, as well as metal strands, as subject of theinvention may e.g. be used to reinforce polymer or rubber belts, such astiming belts, elevator or hoisting belts, conveyor belts, or can be usedfor control cables, elevator or hoisting rope, suspension rope orseveral automotive applications such as tire reinforcement or windowelevator cable.

Since the strands or cords, comprising a strand as subject of theinvention, overcomes the presently known technical drawbacks, the strandor cord manufacturer is also able to reduce the waste-level, and thestrand or cords can be provided in a more economical way. This sincealso a drawback is faced by these manufacturers, being obliged atpresent to provide strands or cords not having filament ruptures overits whole length.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described into more detail with reference tothe accompanying drawings wherein

FIG. 1 is a schematic view of a cord and a strand as subject of theinvention.

FIG. 2 a is a schematic view of a strand having a filament rupture.

FIG. 2 b is a schematic view of the strand of FIG. 2 a, of which thefilament ends are fixed according to the invention.

FIG. 3 is a radial cut according to the plane AA′ of the cord of FIG. 1.

FIG. 4 is a polymer belt comprising a cord as subject of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

An embodiment of a metal cord and a metal strand as subject of theinvention is shown in FIG. 1. A metal cord 100, provided out of steelhaving 0.7% C, having a construction “(0.21+6×0.19)+6×(0.19+6×0.175)”.The cord comprises 7 strands (101 a, 101 b, 101 c, 101 d, 101 e, 101 fand 101 g). each strand comprises a core filament 102 and filaments 103providing the outer layer of the strand.

The core strand 101 a comprising a core filament 102 of diameter 0.21mm, being encircled by 6 filaments 103 of a diameter 0.19 mm. The otherouter strands 101 b, 101 c, 101 d, 101 e, 101 f and 101 g having all acore filament 102 of diameter 0.19 mm, and 6 encircling filaments 103 of0.175 mm.

The core strand 101 a has a lay length of 6.3 mm and the outer strands101 b, 101 c, 101 d, 101 e, 101 f and 101 g having all a lay length 104of 8 mm. The core strand 101 a and the metal cord itself are twisted inthe same direction (S or Z direction) whereas the strands 101 b, 101 c,101 d, 101 e, 101 f and 101 g all being twined in the opposite direction(Z, respectively S).

As shown in FIG. 2 a and FIG. 2 b, the strand 101 d has one filament 105being interrupted. The metal filament 105 is a filament of the outerlayer of strand 101 d. This rupture provides two filament ends 107 a and107 b projecting out of the strand profile as shown in FIG. 2 a.

According to the present invention, both ends 107 a and 107 b are fixed,preferably soldered, too the uninterrupted filaments of the strand 101 dproviding two fixation points 106, as shown in FIG. 2 b. Theinterruption zone of the strand 101 d has a length as indicated witharrow 108. The interruption zone has one filament less, so 6 filamentsremain uninterrupted in the present example.

As fixing substance, preferably soldering substance chosen out of thegroup consisting of Ag, Sn or Ag—Sn alloys is used. Most preferablySn—Ag alloy is used.

As indicated in FIG. 3, being a section according to AA′ of FIG. 1, onenotices that the diameter of the strand 101 d, indicated 301, isessentially equal to the diameter of the location of the fixation points106 at each side of the interruption zone, as indicated with 302.

The force at rupture and the elongation at rupture of the strand 101 dand of the cord 100 are given in Table I. TABLE I Elongation at sampleForce at rupture (Mpa) rupture (%) Strand 101d Sample 1 396.9 1.24Sample 2 415.6 1.36 Sample 3 420.2 1.52 Sample 4 419.4 1.38 Sample 5418.2 1.43 Reference without 488 2.05 soldered zone Cord 100 Sample 13081.5 2.46 Sample 2 3077.5 2.39 Sample 3 3033.6 2.16 Sample 4 3020.22.16 Sample 5 3018.7 2.18 Sample 6 3078.9 2.37 Reference without 32002.75 soldered zone

For all samples, an Ag—Sn alloy soldering substance was used.

All tests are done on a sample of 1000 mm of strand or cord.

As one notice, the average force at rupture of the strands withinterruption zone is 85% of the force at rupture of the reference strandwithout interruption zone. The average elongation at rupture is 68% ofthe elongation at rupture of the reference strand without interruptionzone.

The average force at rupture of the cord comprising a strand withinterruption zone is 95% of the force at rupture of the reference cordcomprising strands without interruption zone. The average elongation atrupture is 82% of the elongation at rupture of the reference cordcomprising strands without interruption zone.

As shown in FIG. 4, metal cords 41 are embedded in a polyurethane matrix42. The metal cord 41 a as subjects of the invention has a strand with asoldered zone 43. Such belt can be used as elevator belt.

1. A metal strand comprising at least two filaments, at least onefilament being interrupted providing at least one filament end,characterized in that said filament end being fixed to the uninterruptedfilaments of said strand using a fixing substance.
 2. A metal strandaccording to claim 1, said strand having an interruption zone, at eachside of said interruption zone, at least one filament end being fixed tosaid uninterrupted filaments.
 3. A metal strand according to claim 1,said fixing substance being a glue.
 4. A metal strand according to claim1, said fixing substance being a polymer.
 5. A metal strand according toclaim 1, said fixing substance being a soldering substance.
 6. A metalstrand according to claim 5, said soldering substance having a meltingtemp lower than 700° C.
 7. A metal strand according to claim 5, saidsoldering substance being chosen out of the group consisting of Ag, Snor Ag—Sn alloys.
 8. A metal strand according to claim 1, only onefilament being interrupted.
 9. A metal strand according to claim 1, saidstrand having a strand diameter, the diameter of the fixation of thefilament ends being essentially equal to said strand diameter
 10. Ametal strand according to claim 1, said strand diameter being smallerthan 5 mm.
 11. A metal strand according to claim 1, said strand diameterbeing smaller than 2.5 mm.
 12. A metal strand according to claim 1, saidfilaments having a filament diameter, said filament diameter beingsmaller than 1.15 mm.
 13. A metal strand according to claim 1, saidfilament diameter being smaller than 0.35 mm.
 14. A metal strandaccording to claim 1, said strand having a force at rupture of more than50% of the force at rupture of a sample of said strand, not comprising afilament end.
 15. A metal strand according to claim 1, said strand withinterruption zone having an elongation at rupture of more than 30% ofthe force at rupture of a sample of said strand, not comprising afilament end.
 16. A metal strand according to claim 1, said metal beingsteel.
 17. A metal cord comprising at least two metal strands, at leastone of said strands being a metal strand as in claim
 1. 18. (canceled)19. Use of a metal strand according to claim 1 for reinforcing polymeror rubber belts or tires.
 20. Use of a metal strand according to claim 1in elevator or hoisting belts.
 21. Use of a metal strand according toclaim 1 in timing belts.
 22. Use of a metal strand according to claim 1to provide a multi-strand cord.
 23. Use of a metal strand according toclaim 1 as hoisting or elevator rope.
 24. Use of a metal strandaccording to claim 1 as control cable.
 25. Use of a metal strandaccording to claim 1 as suspension rope.